The Mutant Mouse Resource Facility will provide projects with various strains of transgenic and knockout mice and radiation chimeras. A single resource facility such as this has several advantages: 1) Breeding animals and therefore offspring will be maintained under uniform environmental conditions; 2) Uniformity of mice will allow direct comparison of results from the four user laboratories; 3) Many strains to be utilized in the four projects are not readily available from commercial sources; 4) Centralized breeding will reduce time and costs needed to generate sufficient numbers of animals for projects. This facility will also be able to generate new strains and crosses of existing strains that might be of research interest to the projects. In addition, the centralized production of radiation chimeras will improve efficiency and insure uniformity of reconstituted mice that will benefit each individual project as well as comparisons of results between projects. A web site will be established to facilitate communication between the facility and project leaders and will allow investigators to easily reserve mice for their experiments. The information on the web site will include strains on hand, number of available breeding units per strain, birth dates of pups, availability of pups from each strain. Monthly meetings between the core director and project leaders will allow for discussion of future needs and match strains and number of breeding units per strain to anticipated needs.